What to do to fix cooling unit not starting up but fan blowing on YORK HVAC?

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What to do to fix cooling unit not starting up but fan blowing on YORK HVAC?

Problem: HVAC cooling blowing but not cooling.

Situation:
I have a York Diamond 90 heating/ac unit for the top two floors of our town home (matched unit for bottom two floors, which works fine). The unit is 11 years old and has been serviced before each heating and cooling season.

About 4-5 years ago we experienced the cooling on the unit would not start up, but the fan would run. Typically the indoor unit would freeze up. The first thing the technician did was add freon. Later the company had us replace the outside compressor. Then a year or so later the problem started again, almost always thetedhnician added freon and it worked, for months. Every summer when really hot outside the same problem would occur, they would add freon and it would again for awhile.

Only think that works, for awhile: if I turn off the switch to blower, the blower shuts off. I let sit for a few minute. Then turn back on and the unit resets and starts to blow cool air ... For about an hour or so ... Then cooling stops and just blows hot air -- until I flip switch again, which I assume resets something.

What we've tried in last month:
1. Had outdoor compressor cleaned -- dramatically improved the strength of the air blowing from the fan
2. Had more freon added -- tested line temp at outdoor unit is something like 56 degrees
3. Change thermostat -- no help
4. Replaced circuit board -- helped for while
5. Wrapped the TXV valve -- no help.
6. Replaced air filter -- no change

Thanks, but why do you think it resets and works when I turn the indoor switch off, then on?

The fault triggers the board to shut down the unit. It's a safety feature. Resetting the board is a bad idea when the fault hasn't been found and corrected first, since it will occur again. Allowing the system to run, even breifly, while a fault condition exists could lead to additional component failures, even to the failure of the safety switch that is locking the board out.

Uumm, no need for personal attacks on how "smart" someone is whe you don't even know them.

And I did trade my original company / technician in for a new one -- late last week. The first tech with my maintenance company, who appeared to be a newbie, said "need to buy whole new system" and gave me number of his sales guy.

The new tech came last week and is coming again tomorrow, after testing, trying a few things (at midnight) and scheduling to come back again after researching. I'm simply trying to understand the problem and potential solutions so I can be better informed.

Uumm, no need for personal attacks on how "smart" someone is whe you don't even know them.

And I did trade my original company / technician in for a new one -- late last week. The first tech with my maintenance company, who appeared to be a newbie, said "need to buy whole new system" and gave me number of his sales guy.

The new tech came last week and is coming again tomorrow, after testing, trying a few things (at midnight) and scheduling to come back again after researching. I'm simply trying to understand the problem and potential solutions so I can be better informed.